During the past week we have had interesting discussions on this blog about a new paper that tries to filter the AMO signal out of the global temperature series. Several commenters thought that the paper contained serious flaws. Among them was Guido van der Werf, who is a scientist working at the Free University in Amsterdam. His research mainly focuses on forest fires and the effects they have on the carbon cycle. Guido is a friend and I greatly appreciate his efforts to replicate the results of the Zhou/Tung paper. He presents his finding in this guest post.

Guest post by Guido van der Werf

In a recent post Marcel Crok highlighted a new paper by Jiansong Zhou and Ka-Kit Tung in the Journal of the Atmospheric Sciences which halved recent anthropogenic warming and indicated no acceleration of anthropogenic warming over the past 100 years. If true, this is obviously a very important finding. The paper followed on two other papers by Lean and Rind (2008) and Foster and Rahmstorf (2011) aiming to disentangle anthropogenic and natural influences seen in the instrumental temperature record. Three different datasets of temperature are shown below.

An interesting new paper (behind paywall) has been accepted for publication in the Journal of the Atmospheric Sciences. The paper by Jiansong Zhou and Ka-Kit Tung of the University of Washington, Seattle is titled “Deducing Multi-decadal Anthropogenic Global Warming Trends Using Multiple Regression Analysis”. This paper will add fuel to the recent discussions about the nature of the global warming trend and whether it recently has stabilized or not. The authors by the way conclude it has not. Their main conclusions however is:

When the AMO is included, in addition to the other explanatory variables such as ENSO, volcano and solar influences commonly included in the multiple linear regression analysis, the recent 50-year and 32-year anthropogenic warming trends are reduced by a factor of at least two. There is no statistical evidence of a recent slow-down of global warming, nor is there evidence of accelerated warming since the mid-20th century.